Total photosynthesis is limited by a range of environmental factors. These include the amount of light available, the amount of leaf area a plant has to capture light (shading by other Plants is a major limitation of photosynthesis), rate at which carbon dioxide can be supplied to the chloroplasts to support photosynthesis, the availability of water, and the availability of suitable temperatures for carrying out photosynthesis.
Light intensity (irradiance), wavelength and temperature
The process of photosynthesis provides the main input of free energy into the Biosphere, and is one of four main ways in which radiation is important for plant life.
The radiation Climate within plant communities is extremely variable, with both time and space.
In the early 20th century, Frederick Blackman and Gabrielle Matthaei investigated the effects of light intensity (irradiance) and temperature on the rate of carbon assimilation.
At constant temperature, the rate of carbon assimilation varies with irradiance, increasing as the irradiance increases, but reaching a plateau at higher irradiance.
At low irradiance, increasing the temperature has little influence on the rate of carbon assimilation. At constant high irradiance, the rate of carbon assimilation increases as the temperature is increased.
These two experiments illustrate several important points: First, it is known that, in general, photochemical reactions are not affected by temperature. However, these experiments clearly show that temperature affects the rate of carbon assimilation, so there must be two sets of reactions in the full process of carbon assimilation. These are the light-dependent ‘photochemical’ temperature-independent stage, and the light-independent, temperature-dependent stage. Second, Blackman’s experiments illustrate the concept of limiting factors. Another limiting factor is the wavelength of light. Cyanobacteria, which reside several meters underwater, cannot receive the correct wavelengths required to cause photoinduced charge separation in conventional photosynthetic pigments. To combat this problem, a series of proteins with different pigments surround the reaction center. This unit is called a phycobilisome.
Carbon dioxide levels and photorespiration
As carbon dioxide concentrations rise, the rate at which sugars are made by the light-independent reactions increases until limited by other factors. RuBisCO, the enzyme that captures carbon dioxide in the light-independent reactions, has a binding affinity for both carbon dioxide and Oxygen. When the concentration of carbon dioxide is high, RuBisCO will fix carbon dioxide. However, if the carbon dioxide concentration is low, RuBisCO will bind oxygen instead of carbon dioxide. This process, called photorespiration, uses energy, but does not produce sugars.
RuBisCO oxygenase activity is disadvantageous to plants for several reasons:
One product of oxygenase activity is phosphoglycolate (2 carbon) instead of 3-phosphoglycerate (3 carbon). Phosphoglycolate cannot be metabolized by the Calvin-Benson cycle and represents carbon lost from the cycle. A high oxygenase activity, therefore, drains the sugars that are required to recycle ribulose 5-bisphosphate and for the continuation of the Calvin-Benson cycle.
Phosphoglycolate is quickly metabolized to glycolate that is toxic to a plant at a high concentration; it inhibits photosynthesis.
Salvaging glycolate is an energetically expensive process that uses the glycolate pathway, and only 75% of the carbon is returned to the Calvin-Benson cycle as 3-phosphoglycerate. The reactions also produce ammonia (NH3), which is able to diffuse out of the plant, leading to a loss of nitrogen. A highly simplified summary is:
The salvaging pathway for the products of RuBisCO oxygenase activity is more commonly known as photorespiration, since it is characterized by light-dependent oxygen consumption and the release of carbon dioxide.
Experiments related to photosynthesis
Experiment to demonstrate Moll’s half-leaf experiment for showing that CO2, light, chlorophyll and water are necessary requirements for photosynthesis:
De-starch a potted plant by putting it in complete darkness for two days.
Fill partly a wide-mouthed bottle with strong solution of caustic potash and fit a split cork on its mouth.
Insert about half of the portion of a leaf of the de-starched plant into the bottle through the split cork.
Place the whole apparatus in light after applying grease on the upper portion of split cork, and test the leaf for stach after about 10 hours.
Portions of the leaf inside the bottle as well as in between the split cork show negative test for starch indicating the absence of photosynthesis while the portions outside the split cork show positive test for starch indicating the presence of process of photosynthesis in this region.
Negative starch test by the leaf portion present inside the bottle indicates that process of photosynthesis is absent in this region. This portion of leaf is getting all the essential requirements, i.e., light, chlorophyll and water except the CO2 because the latter is absorbed by the caustic potash. Thus, it can be concluded that CO2 is necessary for this process.
Negative test of starch, which is also shown by the portion of the leaf present in between the split of the split cork, can be explained that it is due to the lack of CO2 and light, thus indicating that both of them are essential requirements.
Positive test of starch shown by the portions of the leaf present outside the bottle indicates that photosynthesis process is continuously going on there because all the essential requirements, i.e., light, chlorophyll, water and CO2 are readily available to this portion.
That the chlorophyll is also an essential requirement for photosynthesis can be shown by testing starch in a variegated leaf. Only green portions of the leaf show positive starch test.
Experiment to demonstrate that oxygen is evolved during the process of photosynthesis:
Fill the beaker with the water and take an aquatic plant, such as Hydrilla, in the beaker.
Cut the bases of the plants, tie them with a thread and cover them with an inverted funnel in such a fashion that the cut ends of plants are towards the neck of the funnel.
Fill a test tube with the water and invert it on the upper end of the funnel.
Keep the whole apparatus in sunlight and observe for some time.
From the cut ends of the plant some bubbles are coming out continuously and they are collected at the top of the test tube by displacing the water. On testing this gas it is found that it is oxygen.
The liberated gas is oxygen and it is evolved due to the photolysis of water under the process of photosynthesis. The liberated gas comes in the intercellular spaces and ultimately evolves out through the stomata.
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Plants are living organisms that need a variety of environmental factors in order to grow and thrive. Some of the most important factors include light intensity, light quality, carbon dioxide concentration, temperature, water availability, nutrient availability, Soil pH, salinity, plant age, plant Health, pests and diseases, herbicides, pollution, and Climate Change.
Light intensity
Light is essential for photosynthesis, the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen. The amount of light that a plant receives affects its Growth rate, leaf size, and shape. Plants that receive too much light may become scorched or sunburned, while plants that receive too little light may become leggy and weak.
Light quality
In addition to the amount of light, the quality of light is also important for plant growth. Plants need a balance of different wavelengths of light, including red, blue, and green light. Different wavelengths of light are absorbed by different parts of the plant, and each wavelength plays a different role in plant growth. For example, red light is important for promoting stem and leaf growth, while blue light is important for promoting flowering.
Carbon dioxide concentration
Carbon dioxide is a gas that is essential for photosynthesis. The concentration of carbon dioxide in the Atmosphere has been increasing in recent years due to human activities, such as burning fossil fuels. This increase in carbon dioxide concentration has been shown to increase plant growth rates.
Temperature
Temperature is another important environmental factor that affects plant growth. Most plants grow best at temperatures between 60 and 80 degrees Fahrenheit. However, some plants can tolerate a wider range of temperatures, while others are more sensitive to changes in temperature.
Water availability
Water is essential for all living things, including plants. Plants need water to transport nutrients and Minerals from the soil to their leaves, and they also need water to cool themselves down. Plants that do not receive enough water will wilt and eventually die.
Nutrient availability
Plants need a variety of nutrients in order to grow and thrive. Some of the most important nutrients include nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, zinc, boron, molybdenum, and chlorine. Plants can obtain these nutrients from the soil, from water, or from the air.
Soil pH
The pH of the soil is a measure of its acidity or alkalinity. Most plants grow best in soil with a pH between 6 and 7. However, some plants can tolerate a wider range of pH levels, while others are more sensitive to changes in pH.
Salinity
Salinity is the amount of salt in the soil. High levels of salt can damage plant roots and prevent plants from absorbing water. Plants that are grown in Saline Soils may need to be watered more frequently and may also need to be treated with special Fertilizers.
Plant age
The age of a plant can also affect its growth rate and response to environmental factors. Young plants are often more sensitive to changes in environmental conditions than older plants.
Plant health
Plant health is also important for plant growth. Plants that are healthy are better able to withstand environmental stresses, such as drought, heat, and pests.
Pests and diseases
Pests and diseases can damage plants and reduce their growth rate. Some common pests that affect plants include insects, mites, nematodes, and slugs. Some common diseases that affect plants include viruses, bacteria, and Fungi.
Herbicides
Herbicides are chemicals that are used to kill Weeds. Some herbicides can also damage plants, so it is important to use them carefully.
Climate change is a long-term change in the Earth’s climate. Climate change is caused by human activities, such as burning fossil fuels. Climate change is already having a negative impact on plants, and it is expected to have an even greater impact in the future.
In conclusion, plants are affected by a variety of environmental factors. Some of the most important factors include light intensity, light quality, carbon dioxide concentration, temperature, water availability, nutrient availability, soil pH, salinity, plant age, plant health, pests and diseases, herbicides, pollution, and climate change. It is important to understand these factors in order to grow healthy plants.
Factors Affecting Photosynthesis
Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar. The rate of photosynthesis is affected by a number of factors, including:
Light intensity: The amount of light available affects the rate of photosynthesis. In general, the higher the light intensity, the faster the rate of photosynthesis. However, too much light can damage plant cells, so there is an optimum light intensity for photosynthesis.
Carbon dioxide concentration: The concentration of carbon dioxide in the air affects the rate of photosynthesis. In general, the higher the carbon dioxide concentration, the faster the rate of photosynthesis. However, too much carbon dioxide can also damage plant cells, so there is an optimum carbon dioxide concentration for photosynthesis.
Temperature: The temperature affects the rate of photosynthesis. In general, the higher the temperature, the faster the rate of photosynthesis. However, too high a temperature can damage plant cells, so there is an optimum temperature for photosynthesis.
Water availability: Water is essential for photosynthesis. In general, the more water available, the faster the rate of photosynthesis. However, too much water can drown plant cells, so there is an optimum water availability for photosynthesis.
Nutrient availability: Nutrients are essential for plant growth and development. In general, the more nutrients available, the faster the rate of photosynthesis. However, too many nutrients can also damage plant cells, so there is an optimum nutrient availability for photosynthesis.
Pests and diseases: Pests and diseases can damage plant cells and reduce the rate of photosynthesis.
Soil type: The type of soil affects the availability of nutrients and water to plants. In general, well-drained, loamy soils are best for plant growth and photosynthesis.
Air pollution: Air pollution can damage plant cells and reduce the rate of photosynthesis.
Frequently Asked Questions
What are the factors that affect photosynthesis?
The factors that affect photosynthesis are light intensity, carbon dioxide concentration, temperature, water availability, nutrient availability, pests and diseases, soil type, and air pollution.
How does light intensity affect photosynthesis?
Light intensity affects the rate of photosynthesis by providing the energy that plants need to convert carbon dioxide and water into oxygen and sugar. In general, the higher the light intensity, the faster the rate of photosynthesis. However, too much light can damage plant cells, so there is an optimum light intensity for photosynthesis.
How does carbon dioxide concentration affect photosynthesis?
Carbon dioxide concentration affects the rate of photosynthesis by providing the carbon that plants need to build new plant material. In general, the higher the carbon dioxide concentration, the faster the rate of photosynthesis. However, too much carbon dioxide can also damage plant cells, so there is an optimum carbon dioxide concentration for photosynthesis.
How does temperature affect photosynthesis?
Temperature affects the rate of photosynthesis by affecting the rate of chemical reactions. In general, the higher the temperature, the faster the rate of photosynthesis. However, too high a temperature can damage plant cells, so there is an optimum temperature for photosynthesis.
How does water availability affect photosynthesis?
Water availability affects the rate of photosynthesis by providing the water that plants need to carry out photosynthesis. In general, the more water available, the faster the rate of photosynthesis. However, too much water can drown plant cells, so there is an optimum water availability for photosynthesis.
How does nutrient availability affect photosynthesis?
Nutrient availability affects the rate of photosynthesis by providing the nutrients that plants need to build new plant material. In general, the more nutrients available, the faster the rate of photosynthesis. However, too many nutrients can also damage plant cells, so there is an optimum nutrient availability for photosynthesis.
How do pests and diseases affect photosynthesis?
Pests and diseases can damage plant cells and reduce the rate of photosynthesis. This is because pests and diseases can damage the leaves, which are the parts of the plant that carry out photosynthesis.
How does soil type affect photosynthesis?
Soil type affects the rate of photosynthesis by affecting the availability of nutrients and water to plants. In general, well-drained, loamy soils are best for plant growth and photosynthesis.
How does air pollution affect photosynthesis?
Air pollution can damage plant cells and reduce the rate of photosynthesis. This is because air pollution can contain harmful chemicals that can damage the leaves, which are the parts of the plant that carry out photosynthesis.
Which of the following is not a factor affecting photosynthesis?
(A) Light intensity
(B) Carbon dioxide concentration
(C) Temperature
(D) Water availability
The rate of photosynthesis is highest when the light intensity is:
(A) Low
(B) Medium
(C) High
The rate of photosynthesis is highest when the carbon dioxide concentration is:
(A) Low
(B) Medium
(C) High
The rate of photosynthesis is highest when the temperature is:
(A) Low
(B) Medium
(C) High
The rate of photosynthesis is highest when the water availability is:
(A) Low
(B) Medium
(C) High
Which of the following is a product of photosynthesis?
(A) Glucose
(B) Oxygen
(C) Carbon dioxide
(D) Water
Which of the following is a reactant of photosynthesis?
(A) Glucose
(B) Oxygen
(C) Carbon dioxide
(D) Water
Photosynthesis takes place in the:
(A) Chloroplast
(B) Mitochondrion
(C) Nucleus
(D) Cell membrane
The process of photosynthesis is used by plants to:
(A) Produce food
(B) Reproduce
(C) Get rid of waste
(D) Move around
The process of photosynthesis is essential for life on Earth because it:
(A) Produces oxygen
(B) Removes carbon dioxide from the atmosphere
(C) Provides food for plants and animals
(D) All of the above